A local area network (LAN) is a communication network, limited in geographic scope from several meters to several kilometers, that links end-users generally requiring integrated (data/voice/video) services. Satisfying the growing demand for services with conventional LANs is becoming increasingly more difficult because of the restricted communication capacity available on these LANs. For example, LANs operating at speeds up to 10 megabit/sec. are common for interconnecting terminals, intelligent workstations and personal computers to a large host. Even some LANs operating at 50 megabit/sec. are available for interconnecting small numbers of large hosts. However, these speeds are inadequate for a large business with hundreds of employees and numerous host machines and communication needs for facsimile, high resolution graphics and video requiring up to 1 gigabit/sec. transmission capability.
Part of this inadequacy occurs because some network processes, such as switching and transceiving, are performed electronically even when the transmission medium is a fiber optic cable. The speed of electronic processing is substantially slower than the speed of optical processing. In effect, the network processing is not a suitable match to fiber transmission medium.
Another factor impacting communication speed is that signal propagation time for a high speed system is significant when compared to the duration of a packet of information, thereby complicating network synchronization and scheduling.
Recent activity culminating in the development of high bandwidth optical communication components introduces a new perspective not previously encountered with conventional networking, particularly as related to LANs. For instance, bandwidth is virtually unlimited because of the deployment of high capacity single-fiber and multi-fiber optical cables. Accordingly, cable routing costs per unit bandwidth constitute a diminishing portion of the cost of networking. Thus, bandwidth efficiency may be traded off for lower signal processing cost as well as improved reliability and autonomy of communications.
Also, with respect to the above-mentioned factor relating to network synchronization, it is desirable that any accessing and signaling arrangements in a high bandwidth environment allow the transmitters to be asynchronous with respect to each other; in addition, the arrangements should be tolerant of mild asynchronism between any transmitter and its intended receiver. These points are discussed in further detail in the paper entitled "Coding and Decoding for Code Division Multiple User Communications Systems", published in the IEEE Transactions on Communications, Vol. COM-33, No. 4, April, 1985.